Gamma-mangostin, a novel type of 5-hydroxytryptamine 2A receptor antagonist.
Gamma-mangostin, purified from the fruit hull of the medicinal plant Garcinia mangostana caused a parallel rightwards shift of the concentration/response curve for the contraction elicited by 5-hydroxytryptamine (5-HT) in the rabbit aorta (pA2 = 8.2) without affecting the contractile responses to KCl, phenylephrine (alpha1) or histamine (H1). The perfusion pressure response of rat coronary artery to 5-HT (5-HT2A) was reduced concentration dependently by gamma-mangostin (IC50 = 0.32 microM). 5-HT amplified, ADP-induced aggregation of rabbit platelets (5-HT2A) was inhibited by gamma-mangostin (IC50 = 0.29 microM), whereas that induced by thrombin was not affected, nor did gamma-mangostin affect 5-HT-induced contraction of the guinea-pig ileum (5-HT3)in the presence of 5-HT1, 5-HT2 and 5-HT4 receptor antagonists. Furthermore, 5-HT-induced contraction of the rat fundus (5-HT2B) and 5-HT-induced relaxation of the rabbit aorta in the presence of ketanserin (5-HT1) and carbachol-induced contraction of the guinea-pig ileum (muscarinic M3) were not affected by gamma-mangostin (5 microM). Gamma-mangostin inhibited [3H]spiperone binding to cultured rat aortic myocytes (IC50 = 3.5 nM). The Kd for [3H]spiperone binding was increased by gamma-mangostin (3 nM) from 11.7 to 27.4 nM without affecting Bmax. These results suggest that gamma-mangostin is a novel competitive antagonist, free from a nitrogen atom, for the 5-HT2A receptors in vascular smooth muscles and platelets.
Chairungsrilerd
N
N
Department of Pharmaceutical Molecular Biology, Faculty of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.
Furukawa
K I
KI
Ohta
T
T
Nozoe
S
S
Ohizumi
Y
Y
D000818:Animals; D001667:Binding, Competitive; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D017320:HIV Protease Inhibitors / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D010477:Perfusion; D010936:Plant Extracts / Q000494:pharmacology; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D011817:Rabbits; D051381:Rats; D017208:Rats, Wistar; D044402:Receptor, Serotonin, 5-HT2A; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000378:metabolism; D012702:Serotonin Antagonists / Q000494:pharmacology*; D013134:Spiperone / Q000378:metabolism; D014966:Xanthenes / Q000494:pharmacology*; D044004:Xanthones
D017320:HIV Protease Inhibitors; D010936:Plant Extracts; D010975:Platelet Aggregation Inhibitors; D044402:Receptor, Serotonin, 5-HT2A; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D014966:Xanthenes; D044004:Xanthones; D013134:Spiperone; C021053:mangostin